1. Field of the Invention
The present invention relates to a thin-film forming method and a thin-film forming apparatus, and more particularly to a thin-film forming method and a thin-film forming apparatus capable of forming a thin film while evaluating the film characteristics by measuring a Raman spectrum.
2. Description of the Related Art
In recent years, the thin-film forming technique has progressed considerably resulting in a variety of modifications of the thin-film forming apparatus and the thin-film forming method of obtaining a thin film. In particular, a thin-film forming apparatus and a thin-film forming method arranged to employ a new technique for evaluating the thin film have been investigated. An exemplary thin film, a magnetic film and a protective film for use to constitute a magnetic recording medium are described below.
Magnetic recording mediums for magnetic disc apparatuses and those for digital video tape recorders have mainly been magnetic recording mediums, such as magnetic discs or evaporated tapes each incorporating a thin magnetic metal film. The structure of the magnetic recording medium may be described with reference to FIG. 1, which is a schematic cross sectional view showing the structure of the magnetic recording medium.
In general, a magnetic recording medium 101 is, as shown in FIG. 1, structured such that a non-magnetic support member 102 constituted by a polyethylene terephthalate film is formed. A magnetic film 103 constituted by a Fexe2x80x94Co alloy film or the like is formed on the non-magnetic support member 102. Moreover, a protective film 104, such as a carbon film, is formed on the magnetic film 103. In recent years the magnetic film 103 has been protected from damage occurring due to head crush or the magnetic tape has been given wear resistance against sliding with respect to a magnetic head by providing a hard carbon film, that is, a so-called a diamond-like carbon film (hereinafter called a xe2x80x9cDLC filmxe2x80x9d).
One of the methods of evaluating the characteristics of the protective film 104, (such as the DLC film) specifically, a method of estimating the molecular structure and the composition ratio of the protective film 104, employs a Raman spectrum method. The foregoing method can estimate whether or not the crystal structure approximates the diamond structure.
An example of an analysis of the film characteristic by the foregoing Raman spectrum method is described with reference to FIG. 2, which shows an example of a typical Raman spectrometer.
The Raman spectrum method is structured such that a laser beam emitted from a laser-beam oscillator 111 is introduced into a probe 113 through an optical fiber 112. A base 114 is irradiated with the laser beam emitted from the probe 113. A Raman scattered light generated on the base 114 is introduced into a spectrometer 116 through the probe 113 and an optical fiber 115. In a calculating portion 117, a Raman shift is produced. In an example case in which the base 114 is a substrate having a DLC film, the carbon bonded state of the DLC film is a mixture of fine particles of SP2 (planar structure) and SP3 (tetrahedron structure). The Raman shift of the DLC film has a broad peak in the vicinity of 1300 cmxe2x88x921 to 1500 cmxe2x88x921. Since the Raman shift varies with conditions under which the DLC film is manufactured, the Raman spectrum measurement is an effective way to determine the conditions under which the DLC film is formed.
The foregoing method has been employed in the laboratory, but the Raman spectrum measurement been employed only to examine the state of bonding of molecules in a substance for forming a film on an off-line of the manufacturing process.
Off-line measurement has been performed as follows a film, which must be measured, is formed by a vacuum apparatus for forming a thin film. Then, a portion of the formed films is taken out from the film forming apparatus to be placed in a Raman spectrometer, and the measurement is performed. In the foregoing case, a DLC film having a thickness of about 10 nm and formed on a resin film having a thickness of several xcexcm is subjected to a process in which a predetermined point of the DLC film is irradiated with a laser beam for a long time. This results in the quality of the DLC film changed due to heat, and implies that the characteristic of the film cannot sufficiently be evaluated. When the characteristic of the film is inspected off-line, a sample is obtained from a portion of the film; this obtained portion cannot be used as a product because a destructive test is performed.
In a case of the protective film 104 of the magnetic recording medium 101, which is a magnetic tape or the like, a DLC film is continuously formed on the non-magnetic support member 102 constituted by a rolled resin film having the magnetic film 103 formed on it and having a length of tens of thousands of meters. In the foregoing case, all of the factors for maintaining the constant characteristics of the film cannot easily be controlled because a great effort would required be to analyze these factors and the facility required would be too complicated. Therefore, only a minimal number of factors are controlled to maintain the constant characteristics of the film. Other factors which cannot be controlled or factors which cannot be predicted can cause the characteristics of the film to be changed, which might result in a large quantity of defective goods being produced.
Therefore, a thin-film forming method and a thin-film forming apparatus have been required with which the measured characteristics of a thin film can be feedback to the forming conditions while the characteristics of thin film are being measured in a nondestructive manner during the process for forming the thin film.
An object of the present invention is to provide a thin-film forming method and a thin-film forming apparatus with which the measured characteristic of a thin film can be fed back to the forming conditions while the characteristics of the thin film are being measured in a nondestructive manner and during the film forming process.
A thin-film forming method according to the present invention includes a thin-film forming step in which a thin film is formed on a member to be processed in a reduced-pressure atmosphere, the thin-film forming method comprising the steps of: measuring a Raman spectrum of a formed thin film; and controlling film forming conditions in accordance with a result of measurement of the Raman spectrum.
A thin-film forming apparatus according to the present invention is a thin-film forming apparatus incorporating a thin-film forming device for forming a thin film on a member to be processed in a vacuum chamber, the pressure of which has been reduced, the thin-film forming apparatus comprising: a measuring device for measuring a Raman spectrum of a formed thin film, wherein thin-film forming conditions are controlled in accordance with a result of measurement of the Raman spectrum.
The thin-film forming method and the thin-film forming apparatus according to the present invention are able to evaluate the characteristics of a formed thin film in a real-time manner by measuring the Raman spectrum. A result of the measurement of the characteristics of the thin film is immediately fed back to the forming apparatus. Thus, the thin film can always be formed under optimum conditions.
The measurement can be performed without removing a sample; the formed film can completely be used as the product.
If factors which cannot be controlled in the process for forming the thin film or factors which cannot be predicted cause the characteristics of the film to be changed, satisfactory countermeasures can be taken, which result in continuous formation of a thin film having a predetermined quality. For example, a magnetic recording medium having the protective film formed on it can be manufactured in a large quantity, and the possibility that a large quantity of defective goods are continuously manufactured can be eliminated.